With the recent proliferation of wireless communication devices such as mobile phones, pagers, cellular radios, and others, techniques for locating such devices have gained prominence, e.g., for emergency management systems or other applications involving location awareness. Referring to FIG. 1, in known wireless geo-location applications such as Time of Arrival Ranging (TOA-Ranging) or Time Difference of Arrival (TDOA), signal Time-of-Arrival (TOA) measurement is performed at multiple measurement locations (sites) 110-1, 110-2, . . . , 110-p (generally sites 110). At each of these sites, the signal transmitted by a mobile device 120 is processed to yield times of arrival (TOAs), which are used to obtain surfaces of position. Such surfaces include, but are not limited to, circles, ellipses and hyperbolae upon which the signal transmitter (mobile device 120) can be positioned. The equations of these surfaces are used to solve for the transmitter location. The starting point for such geo-location methods is to obtain reliable TOAs for the signals. These TOAs may have some bias, but if the bias is common to all sites, or if the bias can be eliminated using some other a priori information, the TOAs may be used to solve for the transmitter location.
A known technique for geolocation using an ambiguity function is described at Stein, S., “Algorithms for ambiguity function processing,” IEEE Transactions on Acoustics, Speech, and Signal Processing,” vol. ASSP-29, no. 3, June 1981. According to that technique, an unknown TOA τ at a given site 110, corresponding to a transmission from a mobile device 120, and a corresponding unknown signal doppler frequency ω are obtained by determining the arguments that maximize a specified ambiguity function ƒ that is a function of TOA and doppler frequency:
                                          (                                          ω                ^                            ,                              τ                ^                                      )                    =                      arg            ⁢                                                  ⁢                                          max                                  ω                  ,                  τ                                            ⁢                              [                                  f                  ⁡                                      (                                          ω                      ,                      τ                                        )                                                  ]                                                    ,                            (        1        )            
The ambiguity function ƒ may be expressed as:
                              f          ⁡                      (                          ω              ,              τ                        )                          =                                                                        ∑                                  n                  =                  1                                M                            ⁢                                                s                  ⁡                                      (                                          n                      +                      τ                                        )                                                  *                                  r                  ⁡                                      (                    n                    )                                                  ⁢                                  exp                  ⁡                                      (                                                                  -                        j                                            ⁢                                                                                          ⁢                      n                      ⁢                                                                                          ⁢                      ω                                        )                                                                                            .                                    (        2        )            
In equation (2), the sequence s(n) represents the received signal (the signal received at a site 110) and contains a replica of the signal of interest, usually channel impaired and corrupted by noise. The sequence r(n) represents the reference signal; it is the signal that was actually transmitted by the emitter (mobile device 120) and is either determined by some means or known a priori. The symbol “*” denotes complex conjugation, n is the sample index of the discrete-time signal, and M is a number of samples. In equation (2), all signal sequences are complex baseband representations, and this formulation assumes constant doppler and propagation uncertainty over the duration of the received signal. It is assumed that the baseband reference signal at all times can be either determined exactly or is known a priori.